Boring head



March 27, 1945.v F. w. HACK 2,372,376

BORING HEAD F. W. HACK BORING HEAD March 27, 1945.

Filed Aug. 25 1945 4 Sheets-Sheet 2 @MNHN F. W. HACK `BORING HEAD March 27, 1945.

Filed Aug. 25, 1943 4 SheetSSheet 3 F. W. HACK BORING HEAD March 27, 1945.

' Filed Aug. 25, 1943 4 Sheets-Sheet 4 improvements over the Patented Mu. 21, 194s UNITED ST'I'ES` PATENT GFFICE BORING HEAD Frank w. nach, nes Plaines, 111. Application August 25, 194s. serial No. 99,908 6 Claims. (Cl. 'J7-3) My invention relates to an improved boring head adapted particularly as an attachment for universal machines of the type disclosed in my Patent No. 2,181,128 dated November 28, 1939, and the invention concerns particularly various boring head disclosed in my copending application, Serial No. 453,946, filed August '1, 1942 and issued into Patent No. 2,344,039, dated March 14, 1944.

The main object of the invention is to produce a boring head'ormlng an attachment for and driven from a universal machine such as that shown in my patent above referred to, and which will provide for precision feeding of the tool supporting spindle in either direction through a wide range.

The various features of improvement in my invention-will be readily understood from the following specification in connection with the accompanying drawings, in which:

Figure l is a front elevation of the upper part of a universal machine with my improved boring head attached to the master head of the machine;

Figure 2 with the boring head removed;

Figure 3 is an enlarged section on plane lII--III of Figure l;

Figure 4 is a section on plane IV-IV of Figure 3;

Figure 5 is an elevational view partly in section of the right end of the boring head;

Figure 6 is a right end elevation of the boring head with parts of the framework in section;

Figure 'Z is a section on plane VII- VII of Figure 4; and

Figure 8 is a section on plane VIII- VIII of Figure 4.

The boring head comprises a housing I which has the base wall II secured to its rear wall I2, this wall and the base having the passageway I3 therethrough for outward extension of the frusta-conical coupling plug I4 for connecting the boring structure within the housing I0 with a driving source, as will be explained more in detail later. At its inner ends the plug I4 carries a gear I which meshes with a gear I6 keyed to the hub of a bevel gear I1, this hub being rotatable on a pin I8 secured on the base Wall II, as shown in Figures 3 and '1.

Forwardly of the bevel gear I'I the pinion supporting shaft or spindle I9 extends through the housing III and is journalled at its ends in antifriction bearings and 2l, and inwardly from its left end in a bearing 22. The spindle has is a section on plane II-II of Figure l the keyway 28, and adjacent to the bearing 22 a hub 24 is connected to the spindle by a key 25. This hub has the flange 26 to which is secured thebevel gear 21 which is meshed by the bevel pinion I1, so that, upon rotation of the plug I4, the spindle will be rotated. Intermediate its ends the spindle has the threading 28 for engagement by an internally threaded sleeve or nut 29.

Between the end wall 30 of the housing I0 and the bearing 28 is interposed a thrust bearing 3l, and between the bearings 20 and 22 a thrust sleeve 32 surrounds the spindle. Between the hearing 22 and the hub 24 is interposed a thrust collar 33, and a thrust bearing 34 and a collar 35 are interposed between the right end of the hub 24 and the nut 29. At its right end the nut engages a thrust bearing $6 between which and the bearing 2i a thrust sleeve 31 receives the Spindle, while between the bearing 2t and the end wall 38 of the housing is interposed a thrust bearing 39. The nut 29 is thus held against axial movement while the spindle may be shifted axially for feed of tools to work on the work table T of the machine to which the boring head is attached. The spindle has at each end a tool receiving socket 40 so that the boring head may be operated for application to work at either side thereof on the machine table, the thrust on the spindle being taken up by the various thrust bearings.

Keyed on the hub 24 of the gear 21 are the two driving gears 4I and 42 which mesh, respectively with the gears43 and 44 on the countershaft 45 above the spindle i9 and iournaled in anti-friction bearings 46 and 41. Mounted on the countershaft is a cone gear assembly comprising the transmission gears 48, 49, 50, 5I, 52, 53 and 54, these gears meshing, respectively, with the gears 55, 56, 51, 58, 59, and 6I keyed to the threaded nut 29 which engages the threading on the spindle I9. A spacer sleeve 62 is interposed between the housing In and the right end of the cone gear assembly on the countershaft, and another spacer sleeve 63 on the countershaft is interposed between the left end of the cone assembly and the gear 44 to hold the gears 43 and 44 between the sleeve and the housing I0.

The countershaft is driven from the spindle either through the gears 4I-43 or the gears 42--44, and the gears 43 and 44 may be selectively keyed to the countershaft 45 or may be both disconnected from the countershaft. Figures 4 and 8 show the means for controlling the connection of the gears 43 and 44 with the countershaft. At its left end the countershaft has 88 fulcrumed at 88',

the bore 84- into which extends a bar 85 terminating at its outer end in a cylindrical head 86 having a circumferential channel 81 therein for receiving'plns 88 in the arms of a bell ycrank lever this lever, when swung, effecting axial shifting of the bar 65. The bar 85 has a longitudinal slot in register with a slot 1| extending from the bore 84 through the countershaft 45.- An'L-shaped key 12 is fulcrumed at 13 in the slot 1l, a spring 14 tending to swing the free end of the key 12 through the countershaft slot 1|. When the bar 65 is shifted inwardly, the key will project into the keyway 15 of the gear 44 to key this gear to the countershaft and, when the bar is shifted out, the key will engage in the keyway 16 this gear to the countershaft. When the bar is shifted to an intermediate or neutral position, the key will engage in the annular recess 11 between the gears 43 and 44 and neither gear will be keyed to the countershaft and the countershaft will not be rotates, both gears rotating idly on the countershaft. To releasably hold the key in its inner, outer or intermediate position, the lever 69 has a pin 18 extending therefrom for frictionally engaging in detent recesses 19 in a quadrant 80 on the housing I0.

Describing now the means for selectively connecting the transmission gears 48 to 54 with the countershaft for the desired relative rotation of the bushing 29 and the spindle, each of these gears has a keyway 8| for receiving the key 82. The key is fulcrumed at one end in the slot 83 in the bar 84 which extends into the bore 85 in the right end of the countershaft. A spring 86 tends to swing the key with its outer end through the slot 81 in the countershaft for engagement in the keyway 8| of the selected gear when the bar 84 is shifted. Along its outer end the bar 84 has annular teeth 88 engaged by a gear 89 on a shaft 90. 'I'his shaft is journaled in the housing 9| secured to the housing I0 and at its outer end carries a hand wheel 92. By turning this hand wheel the bar will be shifted for engagement of the key 82 in the keyway of the selected transmission gear on the countershaft. Mounted on the countershaft between the gears are guard rings or washers 93 which, upon longitudinal movement of the bar 84, shift and hold the key 82 radially inwardly until it comes into accurate alignment with the keyway in the transmission gear to be connected before the key can enter such keyway, and simultaneous coupling of two of the gears to the countershaft is thus prevented.

'I'he driving gears 4| and 43 -are primarily for differential rotation of the nut and spindle for feed of the spindle to apply a tool thereon into working engagement with a piece of work on the machine table, while the driving gears 42--44 are primarily differential rotation of the nut and spindle for slowly 'withdrawing the tool from the work. On these driving gears, and also on the cone assembly gears, I have directly applied numerals which indicate the number of teeth on the respective gears. The threaded nut will always be rotated into the same direction as the spindle, but at a differential rate. With the setting of the key 12 in engagement with the gear 44, as shown on Figure 4, the spindle, for either direction of rotation thereof, will be fed axially for withdrawal of a tool therein from the work, but if the key 12 is set for engagement with thc gear 43, then the spindle, for either direction of the gear 43 for keying rotated when the spindle I 9 of rotation thereof, will be fed in direction for applying a tool thereon to work.

Let us assume that the spindle is rotating in the direction of the arrow A to apply a tool in the left end thereof to a piece of work on the machine table, and that the transmission gear 44 is keyed to the countershaft, as shown in Figure 4. This gear 44 and the transmission gear 42 driven by the spindle have each 60 teeth, and therefore the countershaft will be driven at the same speed as the spindle but in opposite direction. In the cone assembly on the countershaft; the gear 48 has 60 teeth and the gear 58 on the nut meshed thereby has also 60 teeth, so that when the gear 48 on the countershaft is keyed thereto, the nut will rotate in the same direction as the spindle and at the same speed. and therefore the gear 48 of the countershaftV is the neutral gear, and is designated by N. The gears 50 to 54 on the countershaft to the right of the neutral gear N have each more teeth than the companion gears on the nut, so that when any of these countershaft gears 58 to 54 are keyed to the countershaft, the nut rotates in the same direction as the spindle but at greater speed, so that with right hand threadconnection between the nut and the spindle, the spindle will be fed axially toward the right to carry its tool away from the work.

Gear 48 to the left of the neutral gear N has 59 teeth and meshes the nut gear 55 which has 62 teeth, and therefore when gear 48 is keyed to the countershaft the nut will be rotated in the same direction as the spindle but at less Speed,

and the nut will lag and therefore the spindle will be fed axially toward the left for application of the tool therein to work on the machine table.

Assume that the threading is 5 turns to the inch, then, for each rotation of the spindle in either direction when the nut is at rest, the spindle will be axially fed 1/5 of'an inch. If the hand wheel 92 is turned for-setting of the key 82 for engagement with the transmission gear 48, which is the neutral gear N, then, with the transmission gears 42 and 44 in service, the nut and spindle will rotate in the same direction. Let us assume that this rotation is in the direction of the arrow A shown on the spindle. Then, if the hand wheel 92 is turned for setting of the key 82 for connection of the 61-tooth gear 50 to the countershaft, then this gear, which meshes the 59-tooth gear 51 on the nut, will, for each revolution thereof, rotate the gear 51 one complete revolution plus two teeth, the nut thus having a lead of two teeth over the spindle, resulting in axial shift of the spindle This two-tooth lead of the 59-tooth gear means a lead of 2/5: of a revolution of the nut over the spindle, and as each revolution of the spindle equals one threading turn, or 1/5 of an inch, the axial shift of the spindle toward the right will be .007 inch per revolution. As the key 82 is shifted toward the right, the tooth lead of the nut increases with consequent increase in speed of shift of the spindle 4toward the right. For example, if the 65-tooth gear on the countershaft is keyed thereto, this gear meshing with the 56- tooth gear on the nut, will give the nut a 9- tooth lead over the spindle, which will result in .032 inch of feed per revolution of the spindle toward the right when the spindle is rotating in l the direction of the arrow A. If the direction of rotation of the spindle is reversed (arrow B), while the transmission gears 42 and 44 are in action, the nut will be rotated in the same directoward the right.

' tion as thesplndle but with leads depending upon the tooth differential of the gears 49 toA I4 on the -countershaft and the companion gears on the nut. With such reversal of rotation of the spindle, the axial feed will be toward `the left for withdrawal of a tool in the right end of the spindle from work on the machine table.

If, with the spindle rotating in either direction, and with the transmission gear 44 keyed to the countershaft, the hand wheel 92 is turned for connection of the key 82 with the gear 48 on the countershaft, this gear, with its 59 teeth meshing the (i2-tooth gear 55 -on the nut, the nut will be rotated in the same direction as the spindle but with a three-tooth lag. 1f the spindle is rotating in the direction of the arrow A, this threetooth lag -will result in corresponding axial feed of the spindle toward the left, and if the direction of rotation of the spindle is as indicated by the arrow B, this three-tooth lag will result in axial feed of the spindle toward the right. Thus, by setting movement of the 'countershaft key 82 from the neutral gear N toward the right, the spindle will be shifted axially in tool-withdrawing direction, and when the key is shifted toward the left from neutral for engagement with gear 48, the spindle will be axially fed in toolapplying direction.

Suppose now that the countershaft key 12 is set for connection of the gear 43 with the countershaft. With the gear 43 having 64 teeth and meshed by the spindle gear 4| with 57 teeth, the countershaft will be rotated more slowly than the spindle and in the opposite direction to the extent of seven teeth, so that the countershaft lags the spindle by seven teeth per revolution. On the countershaft, the gear 58 has 64 teeth and meshes the 57-tooth gear 88 on the nut, so that if the countershaft key 82 is set for connec tion of the gear 53, the nut will be rotated in the same direction and at the same speed as the spindle, and therefore this gear 58 is the neu tral gear, N', when the countershaft transmission gear 43 is in service.

Starting with the neutral gear N', the key 82 may be shifted to the left or to the right. Suppose the key is shifted into connection with the gear 52. This gear has 63 teeth, while the nut gear 59 has 58 teeth, a difference of only five teeth. Therefore the 7-tooth lag of the countershaft is not fully neutralized and the nut will have a 2-tooth lag and will rotate correspondingly slower than the spindle but in the same direction, the result being that the spindle is corl respondingly fed axially toward the left when rotating in the direction of the arrow A, or the feed will be toward the right when the rotation is in the direction of the arrow B. As the key is shifted toward the left for connection of the respective transmission gears, the nut lag will be increased for increased feed of the spindle, and when the gear 49 is reached, which gear has 68 teeth meshing with the 68 tooth gear 56 on the nut, the lag will be seven teeth. When the 59- tooth countershaft gear 48 is reached, which gear meshes with the (i2-tooth gear on the nut, the lag of the gear 55 will be the '7-tooth lag of the countershaft plus the 3-tooth differential lag between the gears 48 and 55, with a total 10- tooth lag of the gear .55 and corresponding lag of the nut. Thus, from the neutral gear N with rotation of the nut with the spindle at equal speed, up to the countershaft gear 48, the lag of the nut is progressively increased, and when the gear 48 is in service the corresponding lag would result in .03 inch of axial feed per revolution of the spindle in tool-applying direction.

It, from the neutral gear N', the key 82 is shifted toward the right for connection of the gear 54 with the countershaft, the gear 54 having 65 teeth and the companion nut gear 8| having 56 teeth, this 9-tooth differential will overcome the countershaft '1-tooth lag by two teeth, with the result that the nut will be rotated in the same direction as the spindle, but in the opposite direction for withdrawal shift of the spindle.

Thus, by working to either side of the neutral gear N', the spindle may be fed axially for tool application to work or shifted axially in the opposite direction for withdrawal of the tool from the work.

In order to obtain full uniform progression of spindle feed, some of the gears in a gearing assembly such as shown may have to be of false pitch diameter. In the assembly shown, the gears 42, 44, 49, 58, 56 and 5l would have to be of false pitch diameter.

If no feed of the spindle is desired, the operator may adjust the lever 69 for setting of the key 12 in neutral position in the recess ll between the gears 43 and 48. For fast feed or rapid traverse of the spindle, the operator may control the threaded nut to Figures 3 and 4, a gear 94 is mounted on the right end of the nut 29 and is meshed by a gear 95 on one end of a hub 98 journaled in a bearing 91|, the other end of the hub carrying a bevel pinion 98 engaged by a bevel gear 99 on the shaft |88 which terminates in a hand wheel ll. During automatic control of the nut, this hand wheel rotates therewith, but when hand control is desired, the key 'l2 is set into neutral position to disconnect the nut from the automatic drive, and then by manipulating the hand Wheel the nut can be controlled for the desired speed of the spindle. Figure l shows a universal machine to which my improved boring head may be applied. The construction of this machine is substantially as disclosed in my Patent No. 2,318,938 dated May 11, 1943. Briefly, it comprises a column |82 on which a master head |83 is vertically adjustable as by means of a screw shaft |84 which has the gear |85 thereon driven by pinion |88 on a shaft lill connected with a transmission train |88 extending from reversible driving means (not shown) in the base of the machine. Bolts |88 serve to hold the master head rigidly to the column after vertical adjustment thereof.

J ournaled in the master head is a driving shaft M8, reversibly driven by gearing connected by the shaft H2 with the belt pulley ||3 which is connected by a belt ||4 with the electric motor E mounted on the master head, this motor being of the reversible type. The end of the drive shaft ||8 has a frusta-conical socket ||5 therein and is journaled in bushings ||6 and ill in the front wall of the master head. Re.- ferring to Figures 2 and 3, the front wall of the master head has the annular T-slot ||8 therein for receiving the heads of bolts ||9. Extending from the master head is the centering boss |28 concentric with the drive shaft ||8, the boss receiving the recess |2| in the base wall of the boring head housing to center the housing accurately relative to the drive shaft ||8 in the master head. The bolts ||9 extend through the housing |8 of the boring head and upon tightening of the nuts |22 the boring head is rigidly secured to the master head. By loosening the manually. Referring vertical or angular disposition of the boring head spindle I9. When the boring head is applied to the master head, the frusto-conical driving plug il enters the socket ||5 in the master head drive shaft, and suitable coupling means, such as the key |23 is provided for coupling the plug to the shaft lill. When the boring head is mounted on the master head, it can be adjusted vertically with the head to any position over the machine table, and the motor E can be controlled for rotation of the `boring spindle i9 in either direction and at any desired speed. I

Provision is made for limiting the axial movement oi the spindle. Referring to Figures 3, 4,

and 6, the right end of the spindle has two circumferential grooves |24 and |25 therein, the distance between which determines the distance through which the spindle may be fed in either direction. Mounted on the housing I0 adjacent to the right end Wall 38 thereof is a switch, which is more or less diagrammatically illustrated. A rod |21 extends through the end wall 38 to be slidable therein and when the end of this rod contacts the outer surface oi' the spindle it will be held out for holding the switch button |28 in for control of a circuit |29 associated with the circuit for the motor E on the master head so that the motor will be held connected in circuit for rotation of the spindle. However, when either of the circumferential grooves |24, |25 in the spindle reaches the rod |21, the rod may enter the groove to permit movement of the switch button |28 to control the circuit |25 for stoppage of the motor and rotation of the spindle and consequent axial movement thereof. To restart operation of the spindle,` the switch button may be held in a moment until the rod |21 is withdrawn by the spindle from the respective groove.

I have disclosed a practical and eiiicient embodiment of the features of my invention, but I do not desire to be limited to the exact structure, arrangement and operation shown and described as changes and modifications may be made without departing from the scope of the invention.

What I claim is:

1. A boring head comprising a housing, a spindle extending through said housing and journalecl therein for rotation and for axial movement and adapted to support working tools, a bushing receiving said spindle and having threaded engagement therewith, said bushing being free to rotate relative to said spindle but being held against axial movement, a driving train for said spindle adapted for connection with a driving source for rotation of the spindle, a cone assembly of gears keyed to said bushing, a countershaft having a cone assembly of transmission gears thereon respectively meshing the gears on the bushinga drive gear on the spindle and a drive gear on the countershaft meshed thereby whereby said countershaft will be rotated in a direction opposite to that of the spindle but.` the transmission gears on the countershait will cause rotation of the bushing in the same direction as the spindle, one of the transmission gears on the countersliaft and its companion gear on the bushing being relatively dimensioned to be neutrai, whereby the rotation of the bushing will be at the same speed as that oi the spindle, the

companion gears in the .cone assemblies at one side of the said neutral gears being dimensioned 30 transmission gears the same as that of to cause rotation ot the bushing in the same direction as the spindle but at speeds greater than that ot the spindle whereby the spindle will be axially fed in one direction. companion gears in said cone assemblies at the opposite side oi said neutral gears being dimensioned Iorrotation of the bushing in the same direction as but at less speed than the spindle whereby the spindie will be fed axially `-in the opposite direction.

2. A boring head for a machine of the type referred to, comprising a housing, a spindle extending through the housing and Journaled therein for rotation and for axial movement and adapted to support working tools, a bushing receiving said spindle and having threaded engagement therewith, said bushing being tree to rotate relative to the spindle but being held against axial movement, a driving train for said spindle adapted for connection with a driving source for rotation of the spindle in either direction, a cone assembly of gears keyed to said bushing, a countershaft having a cone assembly of transmission gears thereon respectively meshing with the gears on said bushing, means for selectively connecting the transmission gears with the countershaft, a driving connection between said spindle and said countershaft for rotation of said countershaft in direction opposite to that of the spindle but with the direction of drive of the bus g by the the spindle, said driving connection being adapted to eiect rotation of the countershaft at a speed less than that of the spindle by a predetermined lag, certain intermeshed gears of said cone assemblies being dimensioned to neutralize said lag for ro- 4g whereby, by the selection of said tation of the bushing and spindle at the same speed, and other intermeshed gears of said cone assemblies being dimensioned to either increase or decrease the effect of said .lag on said bushing transmission gears, the speed of rotation of said bushing will be that of the spindle or will either lag or lead the spindle rotation for axial shift of the spindle in corresponding direction.

3. A boring head for a machine of the type referred to, comprising a housing, a. spindle extending through said housing -and journaled therein for rotation and for axial movement and adapted to support working tools, a bushing receiving said spindle and having threaded engagement therewith, said bushing being free to rotate with or relative to said spindle but being held against axial movement, a driving train for said spindle adapted for connection with a driving source for rotation of the spindle in either direction, a cone assembly of gears keyed to said bushing, a countershaft, a cone assembly of transmission gears on said countershaft for respectively meshing the gears on the bushing, two selective driving connections between said spindle and countershaft for driving said countershaft in a direction opposite to that of the spindle with resulting driving of the bushing through the transmission gears in the same direction as the spindle, one of said driving connections being adapted for rotation of selected transmission gears for rotation of said bushing at a faster rate than the spindle whereby the spindle will be axially fed in one direction, the other driving connection being adapted to rotate selected transmission gears for rotation of said bushing at a slower rate than the spindle for axial feed 'of the spindle in the opposite direction.

4. A boring head for a machine of the type re- Ierred to. comprising a housing, a spindle extendgear meshed thereby and adapted to be keyed to ing through said housing and journaled therein for rotation and for axial movement and adapted to support working tools, a bushing receiving said spindle and having threaded engagement therewith, said bushing being free to rotate with vor relativeto said spindle but being held against axial movement, a driving train for said spindle adapted for connection with a driving source for rotation of the spindle in either direction, a cone assembly of gears keyed to said bushing, a countershaft, a cone assembly of transmission gears on said countershaft for respectively meshing the gears on the bushing, two selective driving connections between said spindle and countershaft for driving said countershaft in a direction opposite to that of the spindle with resulting driving of the bushing through the transmission gears in the same direction as the spindle, one of said driving connections being adapted for rotation of selected transmission gears for rotation of said bushing at a faster rate than the spindle whereby the spindle will be axially fed in one direction, the other driving connection being adapted to rotate selected transmission gears for rotation of said bushing at a slower rate than the spindle for axial feed of the spindle in the opposite direction, and means for selectively rendering either of said driving connections active for corresponding rotation of the countershaft or for rendering both driving connections inoperative.

5. A boring head comprising a housing, a spindle extending through said housing and Journaled therein for rotation and for axial movement and adapted to support a working tool, a bushing receiving said spindle and having threaded engagement therewith, said bushing being free to rotate relative to said spindle but being held against axial movement, a driving train for said spindle adapted for connection with a driving source for rotation of the spindle in either direction, a cone the countershaft, said driving connections being dimensioned to cause different rates of rotation of said countershaft, the intermeshed companion gears in said cone assemblies being dimensioned so that when one of said driving connections is in service the bushing rotation will lead the spindle rotation whereby the spindle will be axially shifted in one direction, and when the otherv of said driving connections is in service said bushing rotation will lag behind the rotation of the l spindle for axial shift of the spindle in the opassembly of gears keyed to said bushing, a countershaft, a cone assembly of transmission gears on said countershaft meshing with respective gears on the bushing, two selective driving connections between said spindle andcountershaft for rotation of said countershaft in a direction reverse to that of the spindle but with the rotation of the bushing by the transmission gears being in the same direction as that of the spindle, each of said driving connections comprising a gear keyed to the spindle and a companion posite direction, and means for selectively keying the companion gear of either of said driving connections to the countershait or for disconnecting both companion gears therefrom.

6. A boring head comprising a housing, a spindle extending through said housing and journaled therein for rotation and for axial movement and adapted to support a working tool at either end, a bushing receiving said spindle and having threaded engagement therewith, said bushing being free to rotate on said spindle in either direction but being held against axial movement, a driving train for said spindle adapted for connection with a driving source for rotation of the spindle in either direction, a cone assembly of gears keyed to said bushing, a countershaft having a cone assembly of transmission gears thereon for meshing respectively with the gears on the bushing, two driving connections between said spindle and said countershaft for rotation of said countershaft in a direction opposite to that of the spindle but with rotation of the bushing through said transmission gears in the same diection as the spindle, and means for selectively connecting said driving connections for service or for disconnecting lboth from service, one of said driving connections being adapted when connected in service to eifect rotation of the coun- 4tershaft and selected transmission gears thereon vfor lag rotation of the bushing relative to the spindle rotation for axial shift of the spindle in one direciton, and the other driving connection being effective when in service to rotate said countershaft and selected transmission gears for lead rotation of the bushing relative to the spindle for axial shift of the spindle in the opposite direction.

FRANK W. HACK. 

